Significant Accounting Policies - Textual (Details)								3 Months Ended			12 Months Ended
	May 01, 2024	Oct. 01, 2016	May 03, 2016	Oct. 01, 2015	Oct. 23, 2014 USD ($)	Mar. 20, 2013 USD ($)	Mar. 28, 2012	Dec. 31, 2016 USD ($) Clients reportable_segment	Sep. 30, 2016 USD ($) reportable_segment	Dec. 31, 2015 USD ($) Clients	Dec. 31, 2016 USD ($) Clients investment $ / shares shares	Dec. 31, 2015 USD ($) Clients investment reportable_segment $ / shares shares	Dec. 31, 2014 USD ($) Clients investment $ / shares shares	Mar. 23, 2016	Dec. 31, 2013 USD ($)
Significant Accounting Policies [Line Items]
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability											$ 2,108,000	$ 1,903,000	$ 2,646,000
Impact of Restatement on Earnings Per Share, Basic | $ / shares											$ 0.04	$ 0.04	$ 0.06
Deferred Tax Liability, Prior Period Correction								$ 6,916,000		$ 9,016,000	$ 6,916,000	$ 9,016,000
Increase (Decrease) in Book Overdrafts											$ 7,000	1,000	$ 38,000
Deferred Tax Assets, Gross, Current										14,381,000		$ 14,381,000
Earnings Per Share, Increase (Decrease) Due To Non-Controlling Dividend As A Result Of Redeemable Redemption Value In Excess of Fair Value | $ / shares											$ 0	$ 0	$ 0
Long-Term Growth Rate Assumed in Annual Goodwill Impairment Test		3.00%		3.00%
Debt Issuance Costs, Net								$ 18,420,000		12,625,000	$ 18,420,000	$ 12,625,000
Deferred Tax Assets, Net, Current										$ 263,000		263,000
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability											$ 8,227,000	$ 38,887,000	$ 18,652,000
Clients exceeding consolidated accounts receivable percentage | Clients								0		0	0	0
Number of Reporting Units											31	13
Consolidated accounts receivable percentage								10.00%		10.00%	10.00%	10.00%
Clients exceeding consolidated largest client revenue | Clients											0	0	0
Consolidated largest client revenue											10.00%	10.00%	10.00%
Equity Method Investment, Amount Sold											$ 2
Distributions from non-consolidated affiliates											7,402,000	$ 0	$ 3,409,000
Cost method investments								$ 10,132,000		$ 11,763,000	10,132,000	11,763,000
Goodwill, Impairment Loss											48,524,000	0	0
Business combination, acquisition related costs											2,640,000	2,912,000	$ 6,133,000
Assets								1,577,378,000		1,577,625,000	1,577,378,000	1,577,625,000
Liabilities								$ 2,026,674,000		2,004,246,000	$ 2,026,674,000	$ 2,004,246,000
Stock Issued During Period, Shares, New Issues | shares											0	0	0
Pension expense											$ 10,026,000	$ 6,731,000	$ 7,503,000
Proceeds from Sale of Equity Method Investments											4,023
Equity Method Investment, Realized Gain (Loss) on Disposal											623
Impact of Restatement on Opening Retained Earnings, before Tax															$ 13,568,000
Performance Shares
Significant Accounting Policies [Line Items]
Share-based compensation, gross											$ 140	1,741	3,026
Real Estate Joint Venture [Member]
Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage								30.00%			30.00%
Minimum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life											3 years
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount		5.00%		7.00%
Weighted Average Cost Of Capital, Annual Goodwill Impairment Test		10.39%		8.92%
Maximum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life											7 years
Equity method investment, ownership percentage								50.00%			50.00%
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount		100.00%		100.00%
Weighted Average Cost Of Capital, Annual Goodwill Impairment Test		13.45%		11.95%
Doner
Significant Accounting Policies [Line Items]
Variable interest entity, qualitative or quantitative information, ownership percentage							30.00%
Ownership interest percentage increase on exercise of option							70.00%
Assets								$ 102,456,000		122,558,000	$ 102,456,000	122,558,000
Liabilities								57,622,000		86,047,000	57,622,000	86,047,000
Contingent Payment [Member]
Significant Accounting Policies [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability								$ (9,211)		$ 41,913	$ 7,972,000	36,344,000	$ 16,467,000
Six Point Five Zero Percentage Notes [Domain]
Significant Accounting Policies [Line Items]
Debt Instrument, Interest Rate, Stated Percentage								6.50%			6.50%			6.50%
Six Point Seven Five Percentage Notes [Member]
Significant Accounting Policies [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						6.75%		6.75%			6.75%		6.75%		6.75%
Debt Instrument, Maturity Year						2020
Notes due 2024 [Domain]
Significant Accounting Policies [Line Items]
Debt Instrument, Interest Rate, Stated Percentage								6.50%			6.50%
Interest Expense [Member] | Fixed Payment [Member]
Significant Accounting Policies [Line Items]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability											$ 255,000	$ 2,543,000	$ 2,186,000
Equity Method Investments [Member]
Significant Accounting Policies [Line Items]
Number of investments sold | investment												1
Proceeds from Sale of Equity Method Investments												$ 2,094
Equity Method Investment, Realized Gain (Loss) on Disposal												1,086
Cost-method Investments [Member]
Significant Accounting Policies [Line Items]
Step acquisition gain on sale of ownership percentage											$ 1,309
Cost-method Investments, Realized Gain (Loss)												$ 5,440
Number of investments sold | investment											3	6	2
Proceeds from sale of other investments											$ 4,074	$ 11,364	$ 8,248,000
Quantitative Assessment [Member]
Significant Accounting Policies [Line Items]
Number of Reporting Units												13
Strategic Communications [Member]
Significant Accounting Policies [Line Items]
Goodwill, Impairment Loss								$ 18,893
All Other [Domain]
Significant Accounting Policies [Line Items]
Goodwill, Impairment Loss											$ 29,631,000
All Other [Domain] | Experiential [Member]
Significant Accounting Policies [Line Items]
Goodwill, Impairment Loss									$ 28,000
Reporting Units, Goodwill Impairment Test Performed During Interim Period | reportable_segment									1
All Other [Domain] | Immaterial [Member]
Significant Accounting Policies [Line Items]
Goodwill, Impairment Loss									$ 2,000
Reporting Units, Goodwill Impairment Test Performed During Interim Period | reportable_segment									1
All Other [Domain] | Strategic Communications [Member]
Significant Accounting Policies [Line Items]
Reporting Units Impaired, Annual Goodwill Impairment Test | reportable_segment								1
Wells Fargo Capital Finance, Llc [Member]
Significant Accounting Policies [Line Items]
Debt Instrument, Maturity Date			May 03, 2021		Sep. 30, 2019
Wells Fargo Capital Finance, Llc [Member] | Revolving Credit Facility [Member]
Significant Accounting Policies [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 325,000,000	$ 225,000,000
Scenario, Forecast [Member] | Wells Fargo Capital Finance, Llc [Member] | Six Point Five Zero Percentage Notes [Domain]
Significant Accounting Policies [Line Items]
Debt Instrument, Maturity Year	2024